The prior art embraces units for filling containers with liquid or powder products, equipped with a carousel carrying a plurality of pedestals on which to stand the containers, each associated with a respective dispensing device from which a predetermined quantity of material is dropped into a container placed on the respective pedestal.
The operation of the single dispensing device is governed by respective weighing means coupled to the pedestal and able to sense the weight of the container continuously. At a given moment during the filling step when the weighing means indicate that a predetermined weight has been reached, signifying that the container is full, the dispensing device will interrupt the flow of liquid or powder material, for example by closing a shut-off valve on a feed duct through which the material is dispensed.
As a general rule, weighing means take the form of a dynamometer contained in a respective housing located beneath the pedestal on which the container is placed. The pedestal carries a plunger insertable through a hole in the top of the housing.
Thus, the plunger is located partly within the housing and able to interact with the dynamometer.
Conventional units of the type outlined above are washed down periodically in order to remove any residues of the liquid or powder products with which the containers are filled. In the course of filling operations, more exactly, part of the liquid or powder product can escape from the containers and drop onto the pedestal structure, onto the housing or onto the carousel.
At the end of a given production run, accordingly, nozzles are activated to direct a washing liquid onto the carousel, especially onto those areas where the residues are most heavily concentrated.
The washing process in question is a cause of major drawbacks however, due to the infiltration of washing liquid through the hole in the housing.
In effect, the dynamometer components include a piezoelectric material, and electronic parts that are easily damaged if brought into contact with a liquid.
Furthermore, carousels of the type described above are affected by a serious drawback linked to the structural complexity of the weighing means.
In effect, whenever the load cell of the dynamometer needs replacing or servicing, the entire housing first has to be removed from the carousel, whereupon the housing itself must be opened up in order to remove the dynamometer from the relative enclosure.
This servicing operation, normally a manual procedure, turns out to be particularly expensive and complicated, especially when considering the overall weight of the housing, coupled to the plunger and furnished internally with the load cell and all the electronic componentry of the weighing and filling system.